Destroying vegetation with 4-nitroso 1-piperazinethiocarboxylates



United States Patent 3 198 621 DESTRQYING VEGET ATIbN WITH d-NTTRCSC 1-PIPERAZINETIHOCARBOXYLA'IES John J. DAmico, Charleston, W. Va assignorto Monsanto Company, a corporation of Delaware N0 Drawing. Originalapplication May 25, 1961, Ser. No.

112,510. Divided and this application June 1, 1964, Ser. No. 382,979

6 Claims. (CI. 71-25) This is a division of application Serial No.112,510, filed May 25, 1961.

This invention relates to a new class of piperazines, to the process ofmaking the same, and to the process of destroying or controllingundesired vegetation.

The new compounds possess the structure where X is oxygen or sulfuratleast one of which is sulfur, Y is halogen and n is an integer greaterthan zero but less than five, preferably two or three.

The halogen substituents are preferably chlorine but romine and to alesser extent fluorine and iodine are also suitable. Not more than fourhalogen atoms should be present. Whether the number of halogens is two,three or four, it is preferred that the 2- and 6-positions are occupied:by halogen.

The halobenzyl esters of 4-nitroso l-piperazinecarbothionic acid may beprepared by condensing a halobenzyl xanthate with sodiummonochloroacetate and the product treated with 4-nitrosopiperazine. Thehalobenzyl esters of 4-nitros0 l-piperazinecarbodithioic and 4-nitrosol-piperazinecarbothiolic acids may be prepared by condensing ahalogenated benzyl halide with the carbodithioic or carbothiolic acid.However, the free acids are of limited stability and are preferably usedin the form of their salts. The condensations go readily in aqueousmedium with water soluble salts, as for example alkali metal or ammoniumsalts. Substituted ammonium salts, also known as amine addition salts,can be used as for example, triethylamine, trimethylamine, tributylamineand other tertiary organic amine salts. The acids and salts thereofwhich correspond to the esters also appear to be new compounds. Thecarbodithioic and carbothiolic acids form readily from4-nitrosopiperazine and carbon disulfide or carbonoxysulfide. Asexplained, it is preferred to carry out the condensation in the presenceof either a tertiary organic amine or inorganic base. For example,sodium 4-nitroso 1-piperazinecarbodithioate formed in 100% yield byreacting 0.2 mole each of 4- nitrosopiperazine, carbon disulfide and 25%sodium hydroxide in 200 ml. of water at 5-15 C. The product was a 15.2%solution of the sodium salt. These methods of synthesis are illustrativeonly and other methods can be used wh re desired.

As illustrative of the new compounds there may be mentioned2,3,5,6-tetrachlorobenzy1 4-nitroso-1-piperazinecarbodithioate,2,3,5,6-tetrachlorobenzyl 4-nitroso-1- piperazinecarbothiolate,2,3,5,6-tetrachlorobenzyl 4-nitroso 1epiperazinecanbothionate,2,3,4,5-tetrachlorobenzyl 4-nitroso-1-piperazinecarbodithioate,2,3,4,5,-tetrachlorobenzyl 4-nitroso-1-piperazinecarbothiolate,2,3,4,5-tetrachlorobenzyl 4-nitroso-l-piperazinecanbothionate, 2,3,4-trichlorobenzyl 4 nitroso 1 piperazlnecar bodithioate, 2,3,4,trichloro'benzyl 4 nitroso-1piperaziuecarbothio late,2,3,4-trichlorobenzyl 4-nitroso-1-piperazinecarhothionate,2,3,5,-trichlorobenzyl 4-nitroso-1-piperazinecarbodithioate,2,3,5-trichlorobenzyl 4-nitroso-lpiperazinecarbothiolate, 2,3,5-trichlorobenzyl 4-nitroso-1-pipera- "ice zinecarbothionate,2,3,6-trichlorobenzyl 4-nitroso-1-lpiperazinecarbodithioate,2,3,6-trichlorobenzyl 4-nitroso-1-piperazinecarbothiolate,2,3,6-trichlorobenzyl 4-nitroso-1- piperazinecarbothionate,2,4,5-trichlorobenzyl 4-nitrosol-piperazinecarbodithioate,2,4,5-tn'chlorobenzyl 4-nitroso-l-piperazinecanbothiolate,2,4,5-trichlorobenzyl 4-nitroso-1-piperazinecarbothionate,2,6-dichlorobenzy1 4-nitroso-1-piperazinecahbodithioate,2,6-dichlotrobenzyl 4-nitroso 1spiperazinecanbothiolate, 2,6-dichlorobenzyl 4mitroso-l piperazinecarbothionate, 2,6-dibromobenzyl4-nitroso-1apiperazinecarbodithioate, 2,6-dibromobenzyl4-nitroso-l-piperazinecarbothiolate and 2,6-di-blromobenzyl4-nitroso-1spiperazinecarbothionate.

The detailed examples below illustrate the preparation and properties ofthe new compounds but are not to be taken as limitative.

EXAMPLE 1 To a stirred charge containing 11.6 grams (0.1 mole) of4-nitrosopiperazine, 16 grams (0.1 mole) of 25% sodium hydroxide and 200ml. of water was added dropwise at 5-15 C. 7.6 grams (0.1 mole) ofcanbon disulfide and stirring continued for an additional hour. To thesodium 4-nitroso-1-piperazinecanbodithioate so prepared was added 19.6grams (0.1 mole) of 2,6-dichlorobenzyl chloride in one portion and thereaction mixture stirred at 25-30" C. for 24 hours. After cooling to 5C., the precipitate was collected by filtration, Washed with water untilneutral to litmus and air dried at 2530 C. After recrystallization frombenzene the 2,6- dichlorobenzyl 4-nitroso 1-piperazinecarbodithioate,obtained in 65.5% yield as a white solid, melted at 174- 175 C. Analysisgave 17.9% sulfur compared to 18.3% calculated for C12H1 Cl N3OS EXAMPLE2 In the procedure of Example 1, 23 grams (0.1 mole) of2,3,6-trichlorobenzyl chloride was substituted for the2,6-dichlorobenzyl chloride. The product was cooled to 0 C. and isolatedas described. The 2,3,6-trichlorobenzy14-nitroso-l-piperazinecarbodithioate was a tan solid melting at 203-204C. after recrystallization from dilute acetone solution. The yield was74.5% of theory. Analysis gave 16.5% sulfur compared to 16.7% calculatedfor C H Cl N 0S EXAMLE 3 To a stirred charge containing 13.8 grams (0.12mole) of 4-nitrosopiperazine, 16 grams (0.1 mole) of 25% sodiumhydroxide and 50 ml. of Water was added in 12 min utes at 0-5 C. 7.6grams (0.107 mole) of COS. Next there was added in one portion 23 grams(0.1 mole) of 2,3,6-trichlorobenzyl chloride and stirring continued foran hour at 0-10 C., a second hour at 10-15" C., a third hour at 15-20 C.and for 24 hours at 2530 C. To the reaction mixture was then added 250ml. of water and the solution stirred at 2530 C. for an additional 15minutes. The precipitate was collected by filtration, washed with wateruntil neutral to litmus and air dried at 25-3 0 C. 2,3,6-trichlorobenzyl4-nitr0so-1-piperazinecarbothiolate was obtained as a white solid in57.1% yield. After recrystallization from ethyl acetate the productmelted at l73l75 C. Analysis gave 28.7% chlorine compared to 28.8%calculated for C H Cl N O S.

EXAMPLE 4 Substituting 19.5 grams (0.1 mole) of 2,6-dichlorobenzylchloride for the 2,3,6-trichlorobenzyl chloride in Example 3,2,6-dichlor0benzyl 4-nitroso-l-piperazinecarbothiolate was obtained as awhite solid in 68.5% theory yield. After recrystallization from ethylacetate the product melted at -122 C. Analysis gave 21.2% chlorine, thecalculated value for C H Cl- N O S.'

EXAMPLE The trichlorobenzyl chloride used in the preparation of thisexample may be prepared by the following procedure: Substantially 1500parts by weight of dry toluene was charged into a chlorinator ofsuitable capacity. Substantially parts by weight of iron filings wereadded as catalyst carrier for ring chlorination and chlorine introducedat about C. During the last part of the run the temperture was increasedto about 70 C. in order to keep the mixture fluid and the flow ofchlorine continued until the increase in weight corresponded to thatcalculated for trichlorotoluene. Thus, when the product analyzed 54.8chlorine, the flow of chlorine was interrupted and the trichlorotoluenegiven a 10% caustic wash and filtered through a bed of clay in order toremove the iron. Alternatively, the iron may be removed by distillationof the chlorinated product. The product was then chlorinated at 160 C.in thepresence of ultra violet light until the gain in weight was thatcalculated for trichlorobenzyl chloride. Analysis of the product forchlorine at this point gave 61.8%.

Condensation with 4-nitrosopiperazine was effected as follows: Asolution comprising 11.6 grams (0.1 mole) of 4-nitrosopiperazine, 16grams (0.1 mole) of sodium hydroxide and 200 ml. of water was preparedand 7.6 grams (0.1 mole) of carbon disulfide added dropwise at 5-15" C.The reaction mixture was then stirred at 25- C. for one hour and 20.7grams (0.09 mole) of ar,ar,ar-trichlorobenzyl chloride added in oneportion. The product was then stirred at 2530 C. for 24 hours, ml. ofethyl ether added and the solution cooled to 5 C. The product wascollected by filtration, washed with 200 ml. of water and air dried at2530 C. ar,ar,ar- Trichlorobenzyl 4-nitroso-1-piperazinecarbodithioatewas obtained as a white solid melting at 155-164 C.

EXAMPLE 6 To a stirred charge containing 18.9 grams (0.2 mole) ofchloroacetic acid and 100 ml. of water was added in small portionsenough sodium carbonate to give a pH of 8. After stirring the charge at1520 C. for 15 minutes, 68 grams (0.2 mole) of potassium2,3,6-trichlorobenzylxanthate monohydrate was added in one portion andstirring continued for 1 hour at 2530 C. Then, 34.6 grams (0.3 mole) of4-nitrosopiperazine was added in one portion and the reaction mixturestirred at 2530 C. for 18 hours. The resulting precipitate was collectedby filtration, Washed with water until neutral to litmus and air driedat 2530 C. This precipitate was slurried with 100 ml. of ethyl ether,filtered and air dried at 2530 C. 2,3,6 trichlorobenzyl4-nitroso-1-piperazinecarbothionate was obtained in 68.6% yield as awhite solid melting at 169171 C. after recrystallization from acetone.Analysis gave 9.1% sulfur and 28.7% chlorine compared to 8.7% sulfur and28.8% chlorine calculated for The intermediate potassium2,3,6-trichlorobenzylxanthate monohydrate was prepared by the followingprocedure: A charge comprising 43 grams (0.2 mole) of2,3,6-trichlorobenzyl alcohol and 500 ml. of heptane was heated withstirringto 70 C. The solution was then cooled to 30 C. and 12.6 grams(0.2 mole) of 90% potassium hydroxide added in one portion. Afterstirring at 25-30 C. for 6 hours, 22.8 grams (0.3 mole) of carbondisulfide was added and stirring continued at 2530 C. for an additional18 hours. The precipitate was collected by filtration, washed with 200ml. of ethyl ether and dried at 2530 C. The xanthate was obtained in100% yield as a light yellow solid.

Herbicidal compositions may be prepared by admixing the piperazine witha carrier material in order to provide formulations adapted for readyand efi'icient application in liquid or solid form. Solid compositionsare formulated by mixing the toxicant with a finely divided or granularsolid, as, for example, tricalcium phosphate, calcium carbonate, kaolin,bole, kisselguhr, talc, bentonite, fullers earth, pyrophyllite,diatomaceous earth, calcinated magnesia, volcanic ash, sulfurand thelike inorganic solid materials, and include for example, such materialsof organic nature as powdered cork, powdered wood, and powdered Walnutshells. The preferred solid carriers are the adsorbent clays, e.g.,bentonite These mixtures can be used for herbicidal purposes in the dryform, or, by addition of water-soluble surfactants the dry particularsolids can be rendered wettable by water so as to obtain stable aqueousdispersions or suspensions suitable for use as sprays. The carrier willbe in major proportion and the toxicant, while less than 50% of thecomposition, will be present in herbicidally effective proportion.

Useful properties as herbicides are illustrated by applying thepiperazines as aqueous sprays to germinating seedlings. The activeingredient was emulsified in water and applied to seeded soil at therate of 5 pounds per acre. About fourteen days after application of the.toxicants results were observed and recorded. The number of seedsemerging was converted to weighted herbicidal ratings based on averagepercent germination of any particular seed lot times an injury factor.This evened irregularities of herbicide ratings of seeds which varied inpercent germination. The injury factor took into consideration anyplants not expected to survive. Thus, phytotoxicity rattings were basedon the number of plants which emerged and would survive as observed two.Weeks after planting. Herbicidal ratings were assigned by means of thefollowing conversion scale:

Toxicant Results Observed Moderate phytotoxicity to morning glory,pigweed and soybean.

Severe phytotoxicity to morning glory, sugar beet, crab grass, pigweed,soybean, \vild buckwheat and tomato; moderate phytotoxieity to mustard(radish) and ioxtail.

Severe phytotoxicity to morning glory, sugar beet, pigweed, soybean andtomato.

Severe phytotoxicity to pigweed.

Moderate phytotoxicity to morning glory, pigweed and soybean.

2,0-D ichlorobenzyl 4-nitros0-1- piperazinecarbodithioate.

2,3,6-Trichlorobenzy1 4-nitroso-1- piperazine-carbodithioate.

2,3,6-Trichlor0benzyl 4-nitros0-1- piperazine-enrbothiolate.

2,6-Diehl0robenzy1 4-nitros0-1- piperaziue-carbothiolate.

ar,ar,ar-Triehlorobenzy1 4-m'tros0- l-piperazine-carbodithioate.

Formative effects were exerted in most cases.

Greater efficiency than from surface application results fromincorporating the toxicants into the top layer of soil. Phytotoxicityratings observed by incorporating the piperazines into the surface soilat a concentration of 4 pound per acre are recorded below:

Table II Toxicant Results Observed 2,3,6-Trichlorobenzy1 4-nitroso-1-piperazine-earbodithioate.

Severe phytotoxicity to morning glory, sugar beet, pigweed and soybean;moderate phytotoxicity to wild buckwheat and tomatt.

Severe phytotoxicity to soybean;

moderate phytotoxicity to morning glory, mustard (radish), sugar beetand pigwee 2,3.6-Trichlorobenzy1 4-nitr0so-1- piperazine-earbothiolate.

At 0.15 pound per acre 2,3,6-trichlorobenzyl 4-nitroso-1-piperazinecarbodithioate was still severely toxic to pigweed and soybeanand moderately toxic to morning glory.

The term surfactant as employed in the specification and in the appendedclaims is used as in volume II of Schwartz, Perry and Berchs O'dlfZlCActive Agents and Detergents (1958, lnterscience Publishers, Inc, NewYork), in place of the expression emulsifying agent to connotegenerically the various emulsifying agents, dispersing agents, wettingagents and spreading agents that are adapted to be admixed with theactive compounds of this invention in order to secure better wetting andspreading of the compound in water vehicle or carrier in which it isinsoluble through lowering the surface tension of the water (see alsoFrear, Chemistry of Insecticides, Fungicides and Herbicides, secondedition, page 280). These surfactants include the well-knowncapillary-active substances which may be anion-active (or anionic),cation active (or cationic), or non-ionizing (or non-ionic), which aredescribed in detail in volumes 1 and II of Schwartz, Perry and BerchsSurface Active Agents and Detergents (1958, Interscience Publishers,Inc, New York), and also in the November 1947 issue of Chemicalindustries (pages 81l824) in an article entitled, Synthetic Detergents,by John W. McCutcheon and also in the July, August, September andOctober 1952 issues of Soap and Sanitary Chemicals under the title,Synthetic Detergents. The preferred surfactants are the water-solubleanionic surface-active agents and the water-soluble non-ionicsurface-active agents and set forth in US. 2,846,398 (issued August 5,1958). In general it is preferred that a mixture of water-solubleanionic and water-soluble non-ionic surfactants be employed. Generally,the surfactant will comprise only a small proportion of the composition,say 0.1- 15% by weight of the toxicant. Solution of the toxicant inorganic solvents containing small amounts of surfactant providesversatile herbicidal compositions useiul for direct application to soilor for preparin. aqueous sprays. Emulsifiable concentrates may beprepared by dissolving the toxicant in heavy aromatic naphtha andincorporating about 5% of the total composition of surfactant. Theparticular dosage to be applied in a given situation can be readilydetermined by those skilled in the art by conventional techniques. Itdepends upon the formulation, type of vegetation to be controlled,climatic conditions and the particular toxicant used. Compositionscontaining the active ingredient in a concentration within the range of0.l-15.0% by weight applied to constitute total dosage of activeingredient within the range of 0.1-100 pounds per acre comprise theranges usually employed.

Also, 4-nitroso-1-piperazinethiocarboxylates are useful intermediates.Under basic conditions, as for example by treatment with urea, thenitroso group can be removed. Reduction of the nitroso group in knownmanner leads to hydrazine type compounds.

It is intended to cover all changes and modifications of the examples ofthe invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

What is claimed is:

l. The method of destroying undesired vegetation which comprisesapplying thereto a phytotoxic concentration of a compound of thestructure where R represents the 4-nitroso-l-piperazine group, Y ishalogen and n is an integer at least two but less than five.

2. The method of destroying undesired vegetation which comprisesapplying thereto a phytotoxic concentration of a compound of thestructure References Cited by the Examiner UNITED STATES PATENTS2,690,440 9/54 Himel et a1. 260-268 X 2,744,898 5/56 Harman et al.260--268 X 2,792,394 5/57 Himel et al. 260268 X 2,907,767 10/59 Berg260268 OTHER REFERENCES Kushner et al., Journal Organic Chemistry, vol.13, pp. 144153 (1948).

JULIAN S. LEVITT, Primary Examiner.

1. THE METHOD OF DESTROYING UNDESIRED VEGETATION WHICH COMPRISESAPPLYING THERETO A PHTOTOXIC CONCENTRATION OF A COMPOUND OF THESTRUCTURE